Crystal Engineering of Two Light and Pressure Responsive Physisorbents

An emerging strategy in the design of efficient gas storage technologies is the development of stimuli-responsive physisorbents which undergo transformations in response to a particular stimulus, such as pressure, heat or light. Herein, we report two isostructural light modulated adsorbents (LMAs) containing bis-3-thienylcyclopentene (BTCP), LMA-1 [Cd(BTCP)(DPT)₂ ] (DPT=2,5-diphenylbenzene-1,4-dicarboxylate) and LMA-2 [Cd(BTCP)(FDPT)₂ ] (FDPT=5-fluoro-2,diphenylbenzene-1,4-dicarboxylate). Both LMAs undergo pressure induced switching transformations from non-porous to porous via adsorption of N₂ , CO₂ and C₂ H₂ . LMA-1 exhibited multi-step adsorption while LMA-2 showed a single-step adsorption isotherm. The light responsive nature of the BTPC ligand in both frameworks was exploited with irradiation of LMA-1 resulting in a 55 % maximum reduction of CO₂ uptake at 298 K. This study reports the first example of a switching sorbent (closed to open) that can be further modulated by light.